The present invention relates to an acid zinc alloy electroplating bath and the process of electroplating a zinc alloy onto a conductive substrate using the bath. The acid zinc alloy electroplating bath and process of the present invention is particularly applicable to so-called high speed electroplating operations over a wide current density range such as are encountered in strip plating, wire plating, rod plating, conduit plating, or the like.
Electro-deposited zinc alloy of a semi-bright to a lustrous appearance is desirable to provide a decorative plating appearance while simultaneously imparting excellent corrosion protection. The alloy is deposited on a conductive substrate by means of a zinc alloy electroplating bath, such as a zinc-nickel, zinc-cobalt, or zinc-nickel-cobalt bath, which incorporates brightening agents in amounts effective to provide a ductile, corrosion resistant zinc alloy deposit having a semi-bright to bright appearance.
It will be appreciated by those skilled in the art that zinc alloy baths and processes, for example, white and yellow brass alloys and processes, are not analogous to acid zinc baths and processes. For example, brightening agents which are effective for zinc plating are often not effective for alloys of zinc. Thus, some zinc brighteners and other agents have a harmful influence on zinc alloys causing zinc alloy deposits which are sooty black, nonductile, or poorly adhering. Some zinc brighteners or agents cause high current density burning, prevent codeposition of the alloying metal in sufficient quantities, or provide no brightening effect in the zinc alloy processes. Therefore, it will be further appreciated by those skilled in the art that the bath and electroplating process of the present invention particularly relates to the zinc alloy, rather than zinc, baths and processes.